This invention relates generally to improvements in photographic lenses of the variable focus type. More particularly, this invention relates to a novel photographic lens including means for selecting both end limits of the focus adjustment range to correspond with focus settings desired by the photographer.
Variable focus photographic lenses in general are well known to include one or more lens elements supported within a lens housing for appropriate movement to focus an image with respect to a camera or the like. A focus ring is carried for rotation about the lens housing and is mechanically coupled to one or more of the lens elements for axially displacing the lens elements to adjust the focus setting of the photographic lens. Focus adjustment is normally permitted within a prescribed range typically between an infinite focus setting and a relatively close focus setting, with a control pin on the focus ring being movable between fixed stops on the lens housing to limit rotational movement of the focus ring.
During normal use of the photographic lens, the photographer rotates the focus ring to the appropriate focus setting prior to taking a picture. The proper focus setting, however, must be checked visually, particularly at positions intermediate the infinite and minimum settings either by looking through a viewfinder to determine the image clarity or by inspecting distance index markings normally provided on the lens housing. Unfortunately, the time required to visually check the focus setting may result in the photographer missing rapidly occurring scenes or events.
In some instances, the photographer can anticipate the occurrence of scenes or events at different distances from the camera but lacks the physical ability to adjust the focus setting with sufficient speed to photograph these scenes or events. For example, sports events are typified by action which may occur in rapid sequence and at different distances from the photographer, wherein at least some of these distances can be anticipated in advance. However, in a conventional photographic lens, it has not been possible to focus rapidly from one scene to another, since the time-consuming visual focus check is still required before the picture can be taken.
In one proposed photographic lens construction, apparatus is provided for adjusting one end limit of focus ring rotation, thereby advantageously providing a mechanical stop corresponding with one selected focus setting at which action is anticipated by the photographer. See, for example, commonly assigned and copending U.S. application Ser. No. 440,614, filed Nov. 10, 1982, and entitled PHOTOGRAPHIC LENS WITH VARIABLE RANGE FOCUS ADJUSTMENT. In many instances, however, it is desirable to adjust both ends limits of focus ring rotation to provide two selectively set mechanical stops corresponding with two focus settings at which action is anticipated, in which case the above-cited proposed lens construction is of limited utility.
There exists, therefore, a significant need for an improved photographic lens wherein both end limits to rotation of a focus ring can be quickly and easily adjusted to provide mechanical stops corresponding with two selected focus settings, thereby permitting rapid focus adjustment from any intermediate position to one of the selected settings without requiring a visual focus check before a picture can be taken. The present invention fulfills this need and provides other related advantages.